This study focuses on the basement membrane associated modifications that take place after androgen blockade, by studying some of its main components, through histochemical, immuno-histochemical and Western blotting tests, and its ultrastructural aspects. It was demonstrated that laminin and collagen type IV remain associated with a thickened basement membrane and that there is an apparent increase in heparan sulfate content 21 days after castration. Ultrastructurally, basal lamina appeared extensively folded and pleated. It was also observed that detachment of epithelial cells is not dependent of basal lamina degradation and that the free basal lamina surfaces are folded by the action of adjacent cells. We have also observed some aspects of smooth muscle cell degeneration and death, that lead to modifications of the associated basal lamina. In this case, residual basal lamina also shows extensive folding. The results suggested that degradation of excess basement membrane does not occur or is a very slow process within the period examined, and that basement membrane is left re-organized but ultrastructurally and compositionally unaffected.